US4548174A - Dual plug ignition system - Google Patents
Dual plug ignition system Download PDFInfo
- Publication number
- US4548174A US4548174A US06/655,269 US65526984A US4548174A US 4548174 A US4548174 A US 4548174A US 65526984 A US65526984 A US 65526984A US 4548174 A US4548174 A US 4548174A
- Authority
- US
- United States
- Prior art keywords
- plug
- ignition
- coupled
- plugs
- cylinder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
- F02P15/02—Arrangements having two or more sparking plugs
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
- F02P15/08—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits having multiple-spark ignition, i.e. ignition occurring simultaneously at different places in one engine cylinder or in two or more separate engine cylinders
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P7/00—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices
- F02P7/02—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors
- F02P7/03—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors with electrical means
- F02P7/035—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors with electrical means without mechanical switching means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P9/00—Electric spark ignition control, not otherwise provided for
- F02P9/002—Control of spark intensity, intensifying, lengthening, suppression
- F02P9/007—Control of spark intensity, intensifying, lengthening, suppression by supplementary electrical discharge in the pre-ionised electrode interspace of the sparking plug, e.g. plasma jet ignition
Definitions
- This invention relates to an ignition system, and more particularly, to an ignition system wherein each cylinder has more than one ignition plug for igniting the mixture of air and fuel.
- U.S. Pat. No. 4,177,782 issued to Yoshinari et al teaches an ignition system for an internal combustion engine having two spark plugs in each cylinder wherein each of the spark plugs is fired by one ignition coil. Separate output terminals of a secondary coil of the ignition coil are connected to each of the two plugs. For a distributorless ignition system this would require four double ended coils. For simplicity and reduced cost, it would be desirable to require only two double ended coils for a distributorless ignition system. If the teachings of this patent are used with a distributor, two high voltage post connections for each coil as well as two posts for each cylinder are required. Also, the patent does not teach the simultaneous firing of the two spark plugs in a cylinder.
- U.S. Pat. No. 4,407,259 issued to Abo also teaches using two spark plugs.
- the patent teaches a plasma ignition systemm with a plurality of plasma ignition plugs to eliminate a mechanical distributor for sequentially distributing plasma ignition energy into each plasma ignition plug. When both of the spark plugs break down, only one of the plugs would receive the stored capacitive energy in the ignition system. Again, the patent does not teach particular circuitry for promoting simultaneous firing of two spark plugs in one cylinder.
- An ignition system for an internal combustion engine has an ignition coil with a primary and a secondary winding.
- An ignition control circuit applies a charging current to the primary winding of the ignition coil and interrupts the charging current.
- First and second spark plugs are coupled to the ignition coil through first and second diodes, respectively.
- First and second capacitors are coupled in parallel across the gap of the first and second spark plugs, respectively.
- simultaneous firing of two plugs is promoted by isolating each spark plug gap from the ignition coil with a high voltage diode and having parallel capacitance to each plug gap.
- FIG. 1 is a schematic drawing of an ignition system in accordance with an embodiment of this invention.
- FIG. 2 is an embodiment of this invention similar to FIG. 1 with the addition of more spark plugs.
- an ignition system 10 includes an ignition module 12 coupled to the primary coil 14 of an ignition coil 16.
- a secondary coil 18 of ignition coil 16 has one side grounded and the other side connected to a junction between a diode 20 and a diode 22.
- the other side of diode 20 from the junction is coupled to ground through a gap 24 of a spark plug.
- the other side of diode 22 is coupled to ground to the gap 26 of another spark plug.
- a capacitor 28 is coupled in parallel with gap 24.
- a capacitor 30 is coupled in parallel with the gap 26.
- Capacitors 28 and 30 help to balance the discharge energy between gaps 24 and 26 and have an initial stored energy equal to 1/2 CV 2 , where C is the capacitance and V is the lower breakdown voltage of the two gaps.
- Gaps 24 and 26 are positioned in the same cylinder so as to be optically coupled as indicated by radiation 31. Capacitors 28 and 30 also aid in changing the optical coupling between gaps 24 and 26 by intensifying the discharge and increasing the amount of ultraviolet radiation emitted.
- Diodes 20 and 22 are advantageously high voltage diodes and perform the function of isolating capacitor 28 from gap 26 and isolating capacitor 30 from gap 24. As a result, both capacitors 28 and 30 will charge up to the same approximate voltage which will be approximately equal to that of the gap 24, 26 with the lower breakdown voltage. The conditions at the other gap, which requires a higher breakdown voltage, are constantly changing and therefore exhibit a varying breakdown voltage with time or crank angle. As a result, diodes 20 and 22 allow the charge stored on the capacitor in parallel with the nonfired gap to remain for a sufficient time for the gap to break down.
- the reduction of the charge on the unfired capacitor is believed to resemble the charge decay of a simple resistor capacitor series circuit.
- the plug resistance is assumed to be 5 megohms and the capacitance to be 100 picofarads, the time constant is 5 microseconds.
- Such a system has been operated with a plug gap of about 0.04 inches and a parallel capacitance in the range of 100-200 picofarads.
- Successful spark firings have been done at frequencies from 10 to 50 hertz.
- an ignition system 50 has an ignition module 52 coupled to an ignition coil 54 which in turn is coupled to a plurality of diode spark capacitor combinations 56, 57, 58 and 59.
- the connection of the diode, capcitor and spark gap in each combination is the same as illustrated in FIG. 1.
- the capacitance can be an integral part of the spark plug. The size of such a capacitance can be varied by the configuration of the spark plug and by the type of material chosen as the dielectric.
- An optical coupling effect between the spark plug gaps in the same cylinder aids in the firing of the unfired gap.
- the physical mechanism believed to be responsible for this effect is the emission of ultraviolet radiation from the first gap at breakdown.
- the addition of closely coupled parallel capacitance to each spark gap intensifies the discharge and thereby increases the amount of ultraviolet radiation emitted just after breakdowns of the first gap. A fraction of this radiation illuminates the cathode of the second gap and liberates photoelectrons which aids in reducing the breakdown voltage of the unfired gap toward the alternating current threshold level.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
Abstract
An ignition system for an internal combustion engine has an ignition coil coupled to a first and second spark plug provided for each cylinder. A first diode is coupled in series between the first spark plug and the ignition coil. A second diode is coupled in series between the second spark plug and the ignition coil. A first capacitor is coupled in parallel with the first spark plug. A second capacitor is coupled in parallel with the second spark plug.
Description
1. Technical Field
This invention relates to an ignition system, and more particularly, to an ignition system wherein each cylinder has more than one ignition plug for igniting the mixture of air and fuel.
2. Prior Art
There are known internal combustion engines with dual plugs for each cylinder. An associated distributor has two separate high voltage contacts per cylinder, i.e. one for each plug. Thus each spark plug in a cylinder is energized by a separate ignition system. The two ignition systems are required to guarantee that each spark plug gap will break down and fire upon triggering of the ignition module. A distributorless ignition system (DIS) similarly requires a duplicate ignition system. It would be desirable to provide simultaneous dual plug operation and eliminate one of the ignition systems. These are some of the problems this invention overcomes.
U.S. Pat. No. 4,177,782 issued to Yoshinari et al teaches an ignition system for an internal combustion engine having two spark plugs in each cylinder wherein each of the spark plugs is fired by one ignition coil. Separate output terminals of a secondary coil of the ignition coil are connected to each of the two plugs. For a distributorless ignition system this would require four double ended coils. For simplicity and reduced cost, it would be desirable to require only two double ended coils for a distributorless ignition system. If the teachings of this patent are used with a distributor, two high voltage post connections for each coil as well as two posts for each cylinder are required. Also, the patent does not teach the simultaneous firing of the two spark plugs in a cylinder.
U.S. Pat. No. 4,407,259 issued to Abo also teaches using two spark plugs. The patent teaches a plasma ignition systemm with a plurality of plasma ignition plugs to eliminate a mechanical distributor for sequentially distributing plasma ignition energy into each plasma ignition plug. When both of the spark plugs break down, only one of the plugs would receive the stored capacitive energy in the ignition system. Again, the patent does not teach particular circuitry for promoting simultaneous firing of two spark plugs in one cylinder.
An ignition system for an internal combustion engine has an ignition coil with a primary and a secondary winding. An ignition control circuit applies a charging current to the primary winding of the ignition coil and interrupts the charging current. First and second spark plugs are coupled to the ignition coil through first and second diodes, respectively. First and second capacitors are coupled in parallel across the gap of the first and second spark plugs, respectively.
As a result, only one ignition system is required for operation of the dual spark plugs. This results in reduced complexity and reduced cost. Further, such a connection promotes the simultaneous firing of both spark plugs. If one were to simply connect the output of one coil to the two spark plugs in any cylinder, only one of the plugs would usually fire in any given cycle. This is because the in cylinder conditions at each spark plug gap would be such that one of the two spark plug gaps requires a higher voltage to break down. The plug with the lower break down voltage would therefor fire while the other spark plug gap would most likely remain in an unfired condition.
In accordance with an embodiment of this invention, simultaneous firing of two plugs is promoted by isolating each spark plug gap from the ignition coil with a high voltage diode and having parallel capacitance to each plug gap.
FIG. 1 is a schematic drawing of an ignition system in accordance with an embodiment of this invention; and
FIG. 2 is an embodiment of this invention similar to FIG. 1 with the addition of more spark plugs.
Referring to FIG. 1, an ignition system 10 includes an ignition module 12 coupled to the primary coil 14 of an ignition coil 16. A secondary coil 18 of ignition coil 16 has one side grounded and the other side connected to a junction between a diode 20 and a diode 22. The other side of diode 20 from the junction is coupled to ground through a gap 24 of a spark plug. The other side of diode 22 is coupled to ground to the gap 26 of another spark plug. A capacitor 28 is coupled in parallel with gap 24. A capacitor 30 is coupled in parallel with the gap 26. Capacitors 28 and 30 help to balance the discharge energy between gaps 24 and 26 and have an initial stored energy equal to 1/2 CV2, where C is the capacitance and V is the lower breakdown voltage of the two gaps. Gaps 24 and 26 are positioned in the same cylinder so as to be optically coupled as indicated by radiation 31. Capacitors 28 and 30 also aid in changing the optical coupling between gaps 24 and 26 by intensifying the discharge and increasing the amount of ultraviolet radiation emitted.
The reduction of the charge on the unfired capacitor is believed to resemble the charge decay of a simple resistor capacitor series circuit. For example, if the plug resistance is assumed to be 5 megohms and the capacitance to be 100 picofarads, the time constant is 5 microseconds. Such a system has been operated with a plug gap of about 0.04 inches and a parallel capacitance in the range of 100-200 picofarads. Successful spark firings have been done at frequencies from 10 to 50 hertz.
Referring to FIG. 2, an ignition system 50 has an ignition module 52 coupled to an ignition coil 54 which in turn is coupled to a plurality of diode spark capacitor combinations 56, 57, 58 and 59. The connection of the diode, capcitor and spark gap in each combination is the same as illustrated in FIG. 1. If desired, the capacitance can be an integral part of the spark plug. The size of such a capacitance can be varied by the configuration of the spark plug and by the type of material chosen as the dielectric.
An optical coupling effect between the spark plug gaps in the same cylinder aids in the firing of the unfired gap. The physical mechanism believed to be responsible for this effect is the emission of ultraviolet radiation from the first gap at breakdown. The addition of closely coupled parallel capacitance to each spark gap intensifies the discharge and thereby increases the amount of ultraviolet radiation emitted just after breakdowns of the first gap. A fraction of this radiation illuminates the cathode of the second gap and liberates photoelectrons which aids in reducing the breakdown voltage of the unfired gap toward the alternating current threshold level.
Various modifications and variations will no doubt occur to those skilled in the arts to which this invention pertains. For example, the particular configuration of the ignition coil may be varied from that disclosed herein. These and all other variations which basically rely on the teachings through which this disclosure has advanced the art are properly considered within the scope of this invention.
Claims (4)
1. An ignition system for an internal combustion engine having at least one cylinder comprising:
an ignition coil having a primary winding and a secondary winding, said secondary winding having a first and a second output terminal;
an ignition control circuit for applying a charging current to the primary winding of the ignition coil and for interrupting said charging current;
a first and a second spark ignition plug provided for each cylinder of the engine, each of said ignition plugs having at least one gap formed by first and a second spaced apart electrodes, said first and second plugs being positioned in the cylinder so as to be optically coupled to each other so that ultraviolet radiation from the first plug to fire in the cylinder is coupled to the other plug in the cylinder and aids in the firing of the other plug;
first and second connecting means for connecting said first spaced apart electrode of each gap of said first and second plugs, respectively, to ground;
a first diode coupled between said second electrode of said first plug and said first output terminal of said ignition coil;
a second diode coupled between said second electrode of said second plug and said first output terminal of said ignition coil;
a first capacitor means for providing a capacitance coupled across said first and second spaced apart electrodes of said first spark ignition plug; and
a second capacitor means for providing a capacitance coupled across said first and second spaced apart electrodes of said second spark ignition plug.
2. An ignition system as recited in claim 1 further comprising:
a third spark ignition plug having at least one gap formed by first and second spaced apart electrodes, said third plug being positioned in the cylinder so as to be optically coupled to said first and second plugs so that ultraviolet radiation from the first plug to fire in the cylinder is coupled to the other plugs and aids in the firing of the other plugs in the cylinder;
third connecting means for connecting said first spaced apart electrode of said third plug to ground;
a third diode coupled between said second electrode of said third plug and said first output terminal of said ignition coil; and
a third capacitor means for providing a capacitance coupled across said first and second spaced apart electrodes of said third spark ignition plug.
3. An ignition system as recited in claim 1 wherein said first and second capacitor means are an integral part of said first and second spark ignition plugs, respectively.
4. An ignition system as recited in claim 1 wherein said first and second capacitor means are separate components discrete from said first and second spark ignition plugs.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/655,269 US4548174A (en) | 1984-09-28 | 1984-09-28 | Dual plug ignition system |
JP60142689A JPS6185583A (en) | 1984-09-28 | 1985-07-01 | Igniter for internal combustion engine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/655,269 US4548174A (en) | 1984-09-28 | 1984-09-28 | Dual plug ignition system |
Publications (1)
Publication Number | Publication Date |
---|---|
US4548174A true US4548174A (en) | 1985-10-22 |
Family
ID=24628228
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/655,269 Expired - Fee Related US4548174A (en) | 1984-09-28 | 1984-09-28 | Dual plug ignition system |
Country Status (2)
Country | Link |
---|---|
US (1) | US4548174A (en) |
JP (1) | JPS6185583A (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
USRE34183E (en) * | 1986-02-05 | 1993-02-23 | Electromotive Inc. | Ignition control system for internal combustion engines with simplified crankshaft sensing and improved coil charging |
WO1994009271A2 (en) * | 1992-10-19 | 1994-04-28 | Eugen Plaksin | Multiple spark ignition system integrated head gasket for spark-ignition engine |
US5590629A (en) * | 1995-09-14 | 1997-01-07 | Caterpillar Inc. | Spark ignition system of an internal combustion engine |
US5619975A (en) * | 1994-10-20 | 1997-04-15 | Robert Bosch Gmbh | Method for monitoring operations of an internal combustion engine to detect combustion misses |
US9828967B2 (en) * | 2015-06-05 | 2017-11-28 | Ming Zheng | System and method for elastic breakdown ignition via multipole high frequency discharge |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5337244A (en) * | 1976-09-20 | 1978-04-06 | Mitsubishi Motors Corp | Ignition system for engine |
US4177782A (en) * | 1976-11-01 | 1979-12-11 | Hitachi, Ltd. | Ignition system providing sparks for two ignition plugs in each cylinder from a single ignition coil |
US4203403A (en) * | 1973-04-28 | 1980-05-20 | Nippondenso Co., Ltd. | Ignition device for an internal combustion engine |
US4217873A (en) * | 1977-01-25 | 1980-08-19 | Ngk Spark Plug Co. Ltd. | Ignition circuit for self-purifying creeping discharge spark plugs |
EP0018622A1 (en) * | 1979-05-02 | 1980-11-12 | Heinz Baur | Ignition device for combustion engines, oil and gas burners |
US4407259A (en) * | 1981-01-08 | 1983-10-04 | Nissan Motor Company, Limited | Plasma ignition system for an internal combustion engine |
-
1984
- 1984-09-28 US US06/655,269 patent/US4548174A/en not_active Expired - Fee Related
-
1985
- 1985-07-01 JP JP60142689A patent/JPS6185583A/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4203403A (en) * | 1973-04-28 | 1980-05-20 | Nippondenso Co., Ltd. | Ignition device for an internal combustion engine |
JPS5337244A (en) * | 1976-09-20 | 1978-04-06 | Mitsubishi Motors Corp | Ignition system for engine |
US4177782A (en) * | 1976-11-01 | 1979-12-11 | Hitachi, Ltd. | Ignition system providing sparks for two ignition plugs in each cylinder from a single ignition coil |
US4217873A (en) * | 1977-01-25 | 1980-08-19 | Ngk Spark Plug Co. Ltd. | Ignition circuit for self-purifying creeping discharge spark plugs |
EP0018622A1 (en) * | 1979-05-02 | 1980-11-12 | Heinz Baur | Ignition device for combustion engines, oil and gas burners |
US4407259A (en) * | 1981-01-08 | 1983-10-04 | Nissan Motor Company, Limited | Plasma ignition system for an internal combustion engine |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
USRE34183E (en) * | 1986-02-05 | 1993-02-23 | Electromotive Inc. | Ignition control system for internal combustion engines with simplified crankshaft sensing and improved coil charging |
WO1994009271A2 (en) * | 1992-10-19 | 1994-04-28 | Eugen Plaksin | Multiple spark ignition system integrated head gasket for spark-ignition engine |
WO1994009271A3 (en) * | 1992-10-19 | 1994-06-09 | Eugen Plaksin | Multiple spark ignition system integrated head gasket for spark-ignition engine |
US5619975A (en) * | 1994-10-20 | 1997-04-15 | Robert Bosch Gmbh | Method for monitoring operations of an internal combustion engine to detect combustion misses |
US5590629A (en) * | 1995-09-14 | 1997-01-07 | Caterpillar Inc. | Spark ignition system of an internal combustion engine |
US9828967B2 (en) * | 2015-06-05 | 2017-11-28 | Ming Zheng | System and method for elastic breakdown ignition via multipole high frequency discharge |
Also Published As
Publication number | Publication date |
---|---|
JPS6185583A (en) | 1986-05-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4418660A (en) | Plasma ignition system using photothyristors for internal combustion engine | |
US4448181A (en) | Plasma ignition system for an internal combustion engine | |
GB2085523A (en) | Plasma ignition system | |
EP0513995B1 (en) | A misfire detector for use in internal combustion engine | |
KR960000442B1 (en) | Ionic current sensing apparatus | |
US5189373A (en) | Ignition apparatus for an internal combustion engine with engine cylinder misfiring detector having an ionization current noise filter | |
US4433669A (en) | Plasma ignition system for an internal combustion engine | |
US4388549A (en) | Plasma plug | |
US4004561A (en) | Ignition system | |
US4487192A (en) | Plasma jet ignition system | |
US4004562A (en) | Multiple air gap spark plug having resistive electrode coupling | |
US2864974A (en) | Ignition system for internal combustion engines | |
US4548174A (en) | Dual plug ignition system | |
US4653460A (en) | Ignition system for internal combustion engines | |
US3234430A (en) | Ignition circuit for internal combustion engines which prevents ignition skipping | |
US3885541A (en) | Dual ignition coil for internal combustion engine | |
DE3342723C2 (en) | Ignition device for internal combustion engines | |
GB2149852A (en) | Spark plugs | |
EP0551622B1 (en) | Spark igniting a fuel burner | |
US3394689A (en) | Resonant ignition system | |
US5701077A (en) | Misfire detecting device for gasoline internal combustion engine | |
EP0628719B1 (en) | Ignition apparatus employing a lower voltage capacitor discharge self-triggering circuit | |
US3500808A (en) | Capacitive-discharge ignition system | |
JP2641798B2 (en) | Ion current detector | |
EP0378714A1 (en) | Ignition circuit for internal combustion engine |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: FORD MOTOR COMPANY DEARBORN MICHIGAN A CORP OF DE Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ANDERSON, RICHARD W.;REEL/FRAME:004346/0400 Effective date: 19840921 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 19931024 |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |